Bus turns over and then dies when key released from start position

[ColaVentures]

Hey guys! Super grateful for this site and I've used it a bunch over the years and I finally have a problem that I couldn't find a solution to on this site.

My bus has been sitting for a couple years and I went to start it up again. I usually try to start and run it at least once a month. But this time it was having trouble starting. So I took in the batteries to get tested and they were shot. Replaced them with some big ol batteries that were as powerful as the previous ones but still pretty huge. It started right up after those were in.

Then I changed my oil because we're planning to go on a trip and now... the real mystery.

When the key is turned to start the bus turns on just fine. When I release the key into on position it dies.

Here's what I have done:

1 - checked all the fuses for continuity
2 - checked the solenoids in the electrical compartment (hooked em up to A battery and tested for continuity)
3 - replaces ignition switch
4 - checked for bad wires and loose wires
5 - replaces fuel solenoid

Now I'm at a dead end. I feel like it's probably electrical. I think I'm going to try different batteries?? Not sure where to go from here or what to check next.

Thanks!

[Danjo]

Is this a fuel issue? Is it starving for fuel after startup?

[CHEESE_WAGON]

This sounds suspiciously like a worn-out ignition switch, but you say you've replaced that. Ive seen them lose contact internally under the same circumstances, so logically it would make sense. But did you replace the key cylinder and switch together, or just the switch?

Does it start right back up? If so, gently and gradually release pressure on the key as it slowly comes back to RUN, to see if it makes a difference. Just my $0.02.

If it's gotten to single digit temps in the time it's been sitting, and it's a diesel engine, you could have crap in the lines and filters from fuel gelling.

PS - It would help if we knew what you were working with... Navistar, Blue Bird, Cummins engine, etc.

[magnakansas]

from your description your problem is not the batteries..... could be your ignition switch could be something else.... not enough information... what year? what engine?

william

[ColaVentures]

Originally Posted by CHEESE_WAGON

This sounds suspiciously like a worn-out ignition switch, but you say you've replaced that. Ive seen them lose contact internally under the same circumstances, so logically it would make sense. But did you replace the key cylinder and switch together, or just the switch?

Does it start right back up? If so, gently and gradually release pressure on the key as it slowly comes back to RUN, to see if it makes a difference. Just my $0.02.

If it's gotten to single digit temps in the time it's been sitting, and it's a diesel engine, you could have crap in the lines and filters from fuel gelling.

PS - It would help if we knew what you were working with... Navistar, Blue Bird, Cummins engine, etc.

I replaced the whole cylinder. I will go check for loose wires under the dash later today.

It does start right back up every time. I'll give the key turn trick a try.

How would I go about getting the crap out of the lines? It has gotten cold out here and it has been a couple years. Fuel filter?

The bus is a 1992 Thomas with a 5.9 cummins.

Thanks for the help!

[ColaVentures]

Originally Posted by Danjo

Is this a fuel issue? Is it starving for fuel after startup?

I'm not sure... How can I go about checking that?

[CHEESE_WAGON]

Originally Posted by ColaVentures

I replaced the whole cylinder. I will go check for loose wires under the dash later today.

It does start right back up every time. I'll give the key turn trick a try.

How would I go about getting the crap out of the lines? It has gotten cold out here and it has been a couple years. Fuel filter?

The bus is a 1992 Thomas with a 5.9 cummins.

Thanks for the help!

The old-fashioned way, I'm afraid. At least if it gelled bad enough that it won't even idle. Could also be a clogged filter, if you've run biodiesel. You might try some Diesel 911 in the tank, not sure if it's a wise idea, but maybe throw some in the filter housing / water separator as well?

[JackE]

Sure would be helpful to know what the heck you are working on. There are only about 300 different options for key/tumbler/switch options from the beginning of busses to now. It's very possible if you changed just the key/tumbler assembly you didn't actually change the switch. This sounds like all switch problems to me. Next thing I would start chasing is a ground problem.

[Danjo]

If it does start right back up every time it’s probably not fuel.

[ColaVentures]

Originally Posted by JackE

Sure would be helpful to know what the heck you are working on. There are only about 300 different options for key/tumbler/switch options from the beginning of busses to now. It's very possible if you changed just the key/tumbler assembly you didn't actually change the switch. This sounds like all switch problems to me. Next thing I would start chasing is a ground problem.

It's a 1992 Thomas with a Cummins 5.9.

Where would I start looking for the switch? What does it look like? Is that different than the solenoid?

[ColaVentures]

I changed out the filter today and the fuel looked good. Not sure how to check the fuel quality. But the same exact thing happened... so I think it might be something else

[CHEESE_WAGON]

Originally Posted by ColaVentures

It's a 1992 Thomas with a Cummins 5.9.

1992 Thomas <what>? Therein is where we know what you're working with.

We would love to help you, but unfortunately, Thomas is just the coachwork company. They built their own flat-nose buses called Saf-T-Liners, as well as upfitting conventional bus bodies to incomplete chassis supplied by International, GM, and Ford. So Thomas doesn't necessarily tell us specifically enough.

Unfortunately the 5.9 Cummins doesn't help to narrow it down, because the 5.9 Cummins came in just about everything.

Is this a flatnose bus? If so, front-engine or rear-engine? If so, there should be badges somewhere indicate the series -- Saf-T-Liner is the only flat-nose bus I know to be a Thomas, but I've heard of AmTran, Genesis, and a few other names of similar construction.

If it's a conventional dognose, the hood will likely have badges near the cowl windshield area...

International would be "3800", "3600" or something similar
Ford chassis would be "B800", "B700" or something similar
GM chassis would be "C6000", C7000" or something similar

Once we know whether it is a Saf-T-Liner or one of the dognose buses (which get a little more specific per the chassis on which it was built as to ignition switches and wiring, etc.), we'll be better informed to help you.

You've made 5 posts, so you should be able to upload a pic of your bus if you're not sure?

[ColaVentures]

Sorry about that. It's a flatnose pusher. So a Saf-T liner. Thanks!

[magnakansas]

here is a test for you...
find the shut off solenoid for your engine.. with a piece of string, wire, zip tie... something...wire the linkage for the shut off solenoid to the "run" position...... go turn the key and start the bus... does it stay running? If yes, then cut, undo the wire, string, or zip tie. Most diesels of your vintage have an electric shut off solenoid. I have seen only one with a mechanical shut off linkage.

report back the result.


william

[CHEESE_WAGON]

Originally Posted by magnakansas

here is a test for you...
find the shut off solenoid for your engine.. with a piece of string, wire, zip tie... something...wire the linkage for the shut off solenoid to the "run" position...... go turn the key and start the bus... does it stay running? If yes, then cut, undo the wire, string, or zip tie. Most diesels of your vintage have an electric shut off solenoid. I have seen only one with a mechanical shut off linkage.

MK is likely on the right track here.

Originally Posted by ColaVentures

Sorry about that. It's a flatnose pusher. So a Saf-T liner. Thanks!

You might want to put that in the "Chassis" section on your info, just to clarify for anyone you ask for advice. The more info you put in your bio, the easier it is for everyone when we know what you have without you having to explain.

[Bon Voyage]

I’m not sure if this is the same thing MagnaKansas was getting at but I’d try hot wiring it without the ignition to see if it runs. That’ll tell you if you wired the ignition wrong or if it might be broken. How to Hotwire? I don’t know but on a 1992 shouldn’t be hard... YouTube should have something.

[Lkn4it]

This might be a problem with the oil pressure switch. I do not know if your engine has a safety on the OPS or not. I am not familiar with this engine at all. If there are 3 wires on the OPS, it probably does.

If the OPS does not register oil pressure, or the switch is bad, you will get a start and die situation.

The ignition switch bypasses the OPS until the engine starts and then the fuel shut off solenoid or lift pump runs through the OPS after you go back to run position on the ignition switch.

[turf]

Originally Posted by magnakansas

here is a test for you...
find the shut off solenoid for your engine.. with a piece of string, wire, zip tie... something...wire the linkage for the shut off solenoid to the "run" position...... go turn the key and start the bus... does it stay running? If yes, then cut, undo the wire, string, or zip tie. Most diesels of your vintage have an electric shut off solenoid. I have seen only one with a mechanical shut off linkage.

report back the result.


william

i agree. sounds like the fuel shut off has fried and not turning back on. i replaced my solenoid with an ole fashion shut off cable.

you should be able to manually push the solenoid back in or out.... whichever way it moves, and get it going again, but not be able to shut the motor off, because... its broke. you may be able to pull the solenoid back to shut the motor down.